Power line communications (PLC) generally include the use of AC (alternating current) power lines as a communication channel. These may include power transmission lines typically used to transport AC voltages over short and long distances, and may also include electrical distribution wiring typically found inside homes and other building structures.
Generally, PLC devices may connect to AC power lines through PLC modems. The modems may modulate a carrier used for carrying data over the AC line sent from the PLC devices, and may demodulate the carrier for extracting data received over the AC line for use by the devices. For convenience hereinafter, the data and the carrier may be referred to as a “PLC signal” or “PLC signals”. The modems, which generally require DC voltages for their operation, may include means to allow converting the AC voltage from the AC power lines to DC voltages while allowing modulation and demodulation of the carrier transported over the AC power line.
Modems connected to a same powerline network generally require that transmission of data be synchronized to the AC voltage (or current), hereinafter also AC signal, so that specific transmission parameters may be associated with intervals in the signal to compensate for different noises. Synchronization of data transmission to the AC signal is described in US Patent Publication 2007/0025386 assigned to the common assignees of the present invention and incorporated herein in its entirety by reference. There is disclosed “ . . . a powerline network that includes a number of stations including a central coordinator for coordinating transmissions of each of the stations. Each of the stations is configurable to generate one or more tone maps for communicating with each of the other stations in the powerline network. Each tone map includes a unique set of modulation methods for each tone. Each of the stations is further configurable to generate a default tone map for communicating with each of the other stations, where the default tone map is valid for all portions of a powerline cycle. Each of the stations is further configurable to monitor its bandwidth needs and to request additional bandwidth from the central coordinator”.
Data transmission synchronization to the AC signal is further disclosed in U.S. Pat. No. 8,553,706 also assigned to the common assignees of the present invention and incorporated herein in its entirety by reference. There is disclosed a method for using powerline phases to synchronize scheduling of data transmission on a powerline network. As further disclosed therein, such powerline phases are defined according to zero cross points (zero crossings) of AC current at a low frequency (typically 50-60-Hz). A power unit for synchronizing data transmission to the zero crossings of the AC signal is described in US Patent Application Publication 2011/0175712 A1 also assigned to the common assignees of the present invention and incorporated herein in its entirety by reference. There is disclosed “an AC/DC converter for converting VAC input to DC, a zero cross unit for modulating the AC/DC converter output to facilitate zero crossing detection based on the output, and a high pass filter (HPF) for filtering data signals, where the data signals are transmitted and received on the same medium from which the VAC input is received”.